JP2005303257A - Balanced-to-unbalanced conversion device for high-frequency plasma generation, plasma surface treatment device constituted of the balanced-to-unbalanced conversion device, and plasma surface treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface treatment device and a surface treatment method which inhibits a leakage current at an end part of a coaxial cable in ultra high-frequency power supply to an electrode having a large area, thereby uniformly generating plasma of a VHF zone (30 MHz to 300 MHz) between a pair of electrodes in a vacuum container with high reproducibility to ensure uniform plasma surface treatment with respect to substrates having as a large area as 1 m×1 m. <P>SOLUTION: A plasma surface treatment device and method is constituted of a balanced-to-unbalanced conversion device for high-frequency plasma generation which treats, using plasma, a surface of a substrate 12 disposed at one of a pair of electrodes 2, 4 in a vacuum container 1. And in the balanced-to-unbalanced conversion device, a part of the balanced-to-unbalanced converting device 100 is inserted between power supply places 17a, 17b to the electrodes and a second coaxial cable 109a, and the main part of the device 100 is installed on the atmosphere side. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a surface treatment apparatus and a surface treatment method for performing a predetermined treatment on a surface of a substrate using plasma. In particular, the present invention relates to a surface treatment apparatus using an ultrahigh frequency plasma having a low electron temperature and capable of generating a high density plasma, that is, a plasma generated by a high frequency power having a frequency in the VHF band (30 MHz to 300 MHz) and The present invention relates to a surface treatment method.

  Various kinds of processing are performed on the surface of the substrate using plasma to manufacture various electronic devices. LSI (Large Scale Integrated Circuit), LCD (Liquid Crystal Display) TFT (Thin Film Transistor), amorphous Si solar cell, thin film Already put into practical use in the fields of polycrystalline Si solar cells, photoconductors for copying machines, and various information recording devices. In addition, practical application is also progressing in the field of manufacturing ultra-hard films such as diamond thin films and cubic boron nitride (C-BN).

The above technical fields cover various fields such as thin film formation, etching, surface modification, and coating, all of which utilize the chemical and physical action of reactive plasma. The apparatus and method relating to the generation of the reactive plasma are roughly classified into two typical techniques.

The first representative technique is described in, for example, Patent Documents 1 and 2, and is characterized in that two parallel plate electrodes each consisting of a non-ground electrode and a ground electrode are used as a pair for plasma generation. The second representative technique is described in, for example, Patent Documents 3 and 4, and is characterized in that a ladder electrode and a plate electrode are used as a pair for plasma generation.

Further, as a high-frequency power supply technique, Patent Document 5 describes a technique that uses a balance-unbalance conversion circuit that supplies power having a phase difference of 180 degrees to a plate electrode. Patent Document 6 describes a balance-unbalance conversion device for preventing power loss between an antenna and a coaxial cable in the field of wireless engineering.

The features of the technique described in the above document are roughly as follows. In the technique of Patent Document 1, the distance between two longest points of any two points on the periphery of the surface facing the space where the plasma is generated is a quarter of the wavelength of the high-frequency power. And a plurality of power supply points are set at equal positions. In the technique of Patent Document 2, the position of the power supply point of the non-grounded electrode is set on the side surface of the boundary between the first surface that is in contact with the space where the plasma is generated and the second surface that is the back side of the first surface. It is characterized by being located. The technique of Patent Document 3 is characterized in that the shape of the non-ground electrode is a ladder type (ladder type). In the technique of Patent Document 4, a phase difference between a voltage of power supplied to one power supply point on an electrode and a voltage of the power supplied to at least one other power supply point is changed by time. The distribution of the electric field between the electrodes is averaged, and as a result, the spatial distribution of the plasma intensity is made uniform. Patent Document 5 is characterized in that the phases of the two outputs of the balun are different by 180 degrees and power is supplied to the electrodes via an impedance matching device. The technique of Patent Document 6 relates to a means for preventing leakage current generated at a connection portion between an antenna and a coaxial cable end used in the field of wireless engineering, and is a balanced type such as a super top type, a half-wavelength detour type, and an LC bridge type. It is characterized by using an unbalance conversion device.

JP-A-8-325759 (page 3-9, Fig. 1-4) Japanese Patent Laid-Open No. 2002-12977 (page 5-13, FIG. 1-6) JP-A-4-236811 (page 2-4, Fig. 1-4) Japanese Patent Laid-Open No. 2001-257098 (page 3-8, Fig. 1-3) No. 1-88379 (Fig. 1) Japanese Patent Laid-Open No. 2001-53518 (FIGS. 38, 39, and 43)

The above-mentioned plasma surface treatment technology, that is, the plasma surface treatment apparatus and the plasma surface treatment method, reduce the product cost and increase the area of the product due to the improvement in productivity in any of the industrial fields such as LCD, LSI, electronic copying machine and solar cell. The need for large area, uniformization, and high-speed processing is increasing year by year for improving performance (specifications) such as wall-mounted TV.

Recently, in order to meet the above needs, not only in industry but also in academic societies, both plasma CVD (chemical vapor deposition) technology and plasma etching technology are characterized by high density plasma and low electron temperature (VHF band) Advanced research and development on plasma CVD using a power source of 30 MHz to 300 MHz and a large area and high speed film formation, and a large area and high speed of plasma etching have become active. However, the following problems still exist in the prior art.

(1) The first problem is to increase the area of plasma surface treatment (improvement of productivity and improvement of performance). As an apparatus and method for plasma surface treatment, several types of techniques described above are used. For example, when an a-Si film is manufactured by the conventional VHF plasma technology, assuming that reproducibility is ensured, a film thickness distribution of about ± 10 to 15% and a thickness of about 100 cm × 100 cm are obtained when the substrate area is about 50 cm × 50 cm. The film thickness distribution is about ± 15 to 20%.

In general, in the LCD field, the film thickness distribution ensures reproducibility of about ± 5%, and in the solar cell field, the film thickness distribution ensures reproducibility of about ± 10%. It has become. Therefore, there is a problem that the prior art cannot be practically used for manufacturing a product with a large area of 1 mx 1 m class, which is expected as a plasma application in a power supply frequency of VHF region (30 MHz to 300 MHz).

(2) The second problem is speeding up the surface treatment (improving productivity). The premise is that it is effective to increase the power generation frequency of plasma generation to the VHF band of 30 MHz to 300 MHz in order to speed up the plasma surface treatment technology on the premise of ensuring product quality. It has become. However, when the power supply frequency is increased to the VHF band, there arises a problem that the film thickness distribution is remarkably deteriorated.

The reason is considered as follows. As pointed out in Patent Documents 1, 2, and 4, when the high frequency of the power supply is in the VHF band, the wavelength of the radio wave and the length of the power supply system and the propagation path of the electrode become substantially equal, and the wave interference phenomenon ( It is considered that the spatial uniformity of the plasma density cannot be ensured because the traveling wave of the wave and the reflected wave interfere). Another reason is considered to be due to an increase in impedance in the power propagation path due to the skin effect, which is a phenomenon peculiar to VHF, and its non-uniformity.

In addition to the matters pointed out in Patent Documents 1, 2, and 4, as an essential cause regarding the difficulty in increasing the area, uniformity, and speeding up by the conventional VHF plasma, the following power supply system It is thought that the structural problem of is related.

In the prior art, the connection part between the coaxial cable and the electrode of the constituent member of the output circuit of the power feeding system is formed by connecting lines having different structures. That is, in the prior art, as shown in FIGS. 10 to 12, typical leakage currents caused by differences in transmission characteristics between the coaxial cable and the electrode serving as a load are coaxial in the connection portion between the electrode and the coaxial cable. It occurs on the end face of the outer conductor of the cable. That is, the coaxial cable is an unbalanced transmission line, but the electrode serving as a load has characteristics corresponding to two parallel lines (balanced type). As a result, a leakage current is generated at the connecting portion as shown in FIGS. In addition to the plasma generated between the target pair of electrodes, this leakage current not only causes an abnormal discharge in an unnecessary place and causes a problem of power loss, but also prevents uniformization of the substrate surface treatment by the plasma. It is a factor and a problem. The phenomenon related to the leakage current becomes more prominent than RF (13.56 MHz) when the power supply frequency is in the VHF band.

According to the knowledge of radio engineering, if the balance-unbalance conversion device is inserted between the end of the coaxial cable shown in FIGS. It is possible to suppress the current. However, in the field of plasma surface treatment apparatuses, it is difficult to apply for the following reasons, and no successful examples have been found so far.

For example, in the case of applying the balance-unbalance converter of the super top type shown in FIG. 13 and the half-wavelength bypass type shown in FIG. 14 used in the field of radio engineering to the plasma surface treatment apparatus, it is difficult to refuse practical use. There are the following three problems. The first problem is that the frequency of the power used in the high-frequency plasma surface treatment apparatus is in the region of 13.56 MHz and 30 MHz to 100 MHz, so that the half-wavelength is 11 m (13.56 MHz) and 5 m (30 MHz) to 1. 5m (100MHz), quarter wavelength, 5.5m (13.56MHz) and 2.5m (30MHz) to 0.75m (100MHz), the wavelength is remarkably long. It is extremely difficult to install in a vacuum vessel. When these balance-unbalance conversion devices are forcibly installed in a vacuum vessel, there arises a problem that the size of the vacuum vessel becomes so large that practicality is ignored. The second problem is that high-purity ceramics is used as a dielectric material of the constituent member of the coaxial cable installed in the vacuum vessel used in the plasma surface treatment apparatus in order to prevent the generation of impurities in the vacuum field. Since it is used, it has the characteristic that it is hard to bend. Therefore, the means of reducing the installation location by bending a long object is not effective. The third problem is that, for example, when a half-wavelength bypass type balance-unbalance conversion device is applied to a plasma surface treatment device, a strong abnormal discharge occurs as shown in FIG. Absent. In addition, when an LC bridge type balance-unbalance conversion device is applied to a plasma surface treatment device, as shown in FIG. 12, a strong abnormal discharge occurs between a pair of electrodes, so a ceramic insulator is placed around the electrodes. Measures such as filling are required, and there is no practicality in application to a surface treatment apparatus targeting a large area substrate.

Therefore, in the field of application of conventional plasma surface treatment equipment, it is possible in principle to apply the balance / unbalance conversion equipment such as super-top type, half-wavelength detour path type and LC bridge type to plasma surface treatment equipment. However, the technology that can realize the application has not been developed yet.

As described above, in the prior art, it is still difficult to apply VHF plasma CVD and plasma etching to a large area substrate necessary for improving mass productivity and cost reduction, for example, a large area substrate having a size of 1 m × 1 m class, It seems impossible. Under such circumstances, researches are active in related academic societies such as the Japan Society of Applied Physics and the Institute of Electrical Engineers of Japan, but a successful example of a surface treatment method using VHF plasma and its apparatus for a 1 mx 1 m class large area substrate has been announced. It has not been.

Accordingly, the present invention has been made to solve the above-mentioned problems, and plasma surface treatment is performed on balance-unbalance conversion devices such as super-top type, half-wavelength detour type, and LC bridge type used in wireless engineering. By making it applicable to an apparatus, plasma that has been regarded as difficult by the prior art, for example, a high-speed and uniform plasma using a frequency in the VHF band (30 MHz to 300 MHz) even for a large area substrate of 1 mx 1 m class. An object is to provide a surface treatment apparatus and a plasma surface treatment method.

In order to achieve the above object, according to the first aspect of the present invention, a vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, and a substrate are set. Used in combination with a pair of electrodes composed of a first electrode and a second electrode disposed opposite to the first electrode, a power supply system for supplying high-frequency power to the pair of electrodes, and the power supply system A plasma generation balance-unbalance conversion apparatus for use in a plasma surface treatment apparatus that includes a balance-unbalance conversion apparatus and that uses the generated plasma to treat the surface of a substrate, and has a length on the feeding end side of the coaxial cable. A super-top type balance-unbalance converter having a structure in which a cylindrical conductor having a quarter of the wavelength of the high-frequency power is covered and the center of the bottom of the cylindrical conductor is in close contact with the outer conductor of the coaxial cable. Divide One of the supper top type balance-unbalance conversion devices arranged inside the vacuum vessel, the other is arranged on the atmosphere side, and both are connected via a coaxial cable connection terminal attached to the wall of the vacuum vessel It is characterized by having a configuration in which the length adjusting means is provided in the split-top type balun that is connected to the original state and arranged on the atmosphere side.

Similarly, in order to achieve the above object, the invention according to claim 2 of the present application is that a vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, and a substrate are set. A pair of electrodes composed of a first electrode and a second electrode disposed opposite to the first electrode, a power supply system for supplying high-frequency power to the pair of electrodes, and a combination of the power supply system A balanced / unbalanced conversion apparatus for plasma generation used in a plasma surface treatment apparatus having a balanced / unbalanced conversion apparatus to be used and processing the surface of a substrate by using generated plasma, which is disposed on the wall of the vacuum vessel And a metal core rod used in combination with the flange, a first dielectric, a first tubular conductor, a second dielectric, a second tubular conductor, and a third dielectric. Coaxial cable connection end for vacuum equipment A core wire and an external conductor at one end of the first coaxial cable surrounded by the third tube type conductor are connected to the metal core rod and the first tube type conductor on the vacuum side surface, respectively. One end of the third tube-type conductor is connected to the second tube-type conductor on the vacuum side surface of the vacuum device coaxial cable connection terminal, and the vacuum device coaxial cable connection terminal A core wire and an outer conductor at one end of a second coaxial cable surrounded by a metal core rod and a first tubular conductor on the air side surface, respectively, surrounded by a fourth tubular conductor and a cylindrical conductor, respectively. Is connected, and one end of the fourth tubular conductor is connected to the second tubular conductor on the atmospheric side of the coaxial cable connecting terminal for vacuum apparatus, The other end and one end of the cylindrical conductor are in close contact with each other so as to have a relationship between an inner cylinder and an outer cylinder. The other end of the conductor is in close contact with the outer conductor of the second coaxial cable, and the distance from the end surface of the first coaxial cable to the flange and the end surface of the third tubular conductor The other end of the third tubular conductor is arranged so that the distances to the flanges are equal and the outer conductor of the first coaxial cable and the third tubular conductor are not short-circuited. The distance from the end of the cylindrical conductor to the closed end face of the cylindrical conductor is set to a quarter of the wavelength of the high-frequency power, and the core wire and the outer conductor at the other end of the second coaxial cable It is characterized by having a configuration in which the other core wire and the outer conductor of the first coaxial cable are used as the input section and the output section as the output section.

Similarly, in order to achieve the above object, the invention according to claim 3 of the present application is a set of a vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, and a substrate. A pair of electrodes composed of a first electrode and a second electrode disposed opposite to the first electrode, a power supply system that supplies high-frequency power to the pair of electrodes, and a combination of the power supply system A balanced / unbalanced conversion apparatus for plasma generation used in a plasma surface treatment apparatus having a balanced / unbalanced conversion apparatus to be used and processing the surface of a substrate by using generated plasma, which is disposed on the wall of the vacuum vessel Flange, a metal core rod used in combination with the flange, a first dielectric, a first tubular conductor, a second dielectric, and a second tubular conductor in close contact with the flange Coaxial casing for vacuum equipment A core wire at one end of the first coaxial cable surrounded by the second tube-type conductor, respectively, on the metal core rod and the first tube-type conductor on the vacuum side surface of the bull connecting terminal; An external conductor is connected to the metal core rod and the first tubular conductor on the atmospheric side of the coaxial cable connection terminal for the vacuum device, respectively, with the second tubular conductor and the cylindrical conductor, respectively. The core wire and the outer conductor at one end of the enclosed second coaxial cable are connected, and the end of the second tubular conductor and the open end of the cylindrical conductor are connected to the inner cylinder and the outer The cylindrical conductor is in close contact with the cylindrical conductor, the central portion of the bottom surface of the cylindrical conductor is in close contact with the outer conductor of the second coaxial cable, and the distance from the end surface of the first coaxial cable to the flange The distance from the end face of the second tubular conductor to the flange is equal, and the The outer conductor of one coaxial cable and the second tubular conductor are arranged so as not to be short-circuited, and from the open end surface of the second tubular conductor to the bottom surface of the cylindrical conductor The distance is set to a quarter of the wavelength of the high-frequency power supplied from the high-frequency power source, and the core wire and the external conductor at the other end of the second coaxial cable are used as the input unit, and the first The other core wire and the outer conductor of the coaxial cable are used as an output part.

Similarly, in order to achieve the above object, the invention according to claim 4 of the present application is that a vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, and a substrate are set. A pair of electrodes composed of a first electrode and a second electrode disposed opposite to the first electrode, a power supply system that supplies high-frequency power to the pair of electrodes, and a combination of the power supply system A plasma generation balance / unbalance conversion apparatus for use in a plasma surface treatment apparatus having a balance / unbalance conversion apparatus to be used and processing the surface of a substrate using the generated plasma. A core wire at one end of each of the coaxial cables is connected to a power supply point provided at the pair of electrodes, and an outer conductor of each of the coaxial cables at the ends is short-circuited. The other end The core wire and the external conductor are each provided with means for supplying electric power via a coaxial cable connection terminal disposed on the wall of the vacuum vessel and setting the phase difference of the voltage of the electric power to 180 degrees. It is characterized by that.

Similarly, in order to achieve the above object, the invention according to claim 5 of the present application is a set of a vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, and a substrate. A pair of electrodes composed of a first electrode and a second electrode disposed opposite to the first electrode, a power supply system for supplying high-frequency power to the pair of electrodes, and a combination of the power supply system A balanced / unbalanced conversion apparatus for plasma generation used in a plasma surface treatment apparatus having a balanced / unbalanced conversion apparatus to be used and processing the surface of a substrate by using generated plasma, which is disposed on the wall of the vacuum vessel One end portion of the first coaxial cable having a length L is connected to the atmospheric side surface of the first coaxial device connection terminal for vacuum device, and the other end portion of the first coaxial cable is for the coaxial cable. First output terminal of turnout Connected to the second output terminal of the coaxial cable branching unit, a length equal to a value obtained by adding a length L of the first coaxial cable to a half of the wavelength λ of the high-frequency power, that is, ( λ / 2 + L) one end of the second coaxial cable is connected, and the other end of the second coaxial cable is disposed on the wall of the vacuum vessel. Connected to the atmospheric side of the terminal, one end of the third coaxial cable is connected to the input terminal of the coaxial cable branch, and the core wire and external conductor of the other end of the third coaxial cable are input One end of the fourth and fifth coaxial cables having the same length are connected to the vacuum side surfaces of the first and second vacuum device coaxial cable connection terminals, respectively. Each of the outer conductors at the other end of the coaxial cable 5 It is short-circuited by a short-circuiting conductor having a length of one-third or less of the wavelength of wave power, and each core wire at the end of the fourth and fifth coaxial cables is used as an output unit. It is characterized by that.

Here, L can be selected to have an arbitrary length including zero, but if it is zero, a special connector is required. If the length is long, power loss occurs and a large installation location is required.

Similarly, in order to achieve the above object, the invention according to claim 6 of the present application is that a vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, and a substrate are set. A pair of electrodes composed of a first electrode and a second electrode disposed opposite to the first electrode, a power supply system that supplies high-frequency power to the pair of electrodes, and a combination of the power supply system A balanced / unbalanced conversion apparatus for plasma generation used in a plasma surface treatment apparatus having a balanced / unbalanced conversion apparatus to be used and processing the surface of a substrate by using generated plasma, which is disposed on the wall of the vacuum vessel The first output terminal of the coaxial cable branch is connected to the atmospheric side of the first coaxial cable connection terminal for the vacuum device, and the length of the high frequency power is connected to the second output terminal of the coaxial cable branch ½ of wavelength λ One end of a second coaxial cable that is one is connected, and the other end of the second coaxial cable is connected to the atmosphere of the second coaxial cable connection terminal for a vacuum apparatus disposed on the wall of the vacuum vessel. Connected to the side surface, one end of the first coaxial cable is connected to the input terminal of the branching device for coaxial cable, the core wire and the outer conductor of the other end of the first coaxial cable are used as the input unit, One ends of third and fourth coaxial cables having the same length are connected to the vacuum side surfaces of the first and second vacuum device coaxial cable connection terminals, respectively, and the third and fourth coaxial cables are connected. Each outer conductor of the other end of the cable is short-circuited by a short-circuiting conductor having a length of one-third or less of the wavelength of the high-frequency power, and ends of the third and fourth coaxial cables That each core wire has an output part Features.

Similarly, in order to achieve the above object, an invention according to claim 7 of the present application is that a vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, and a substrate are set. A pair of electrodes composed of a first electrode and a second electrode disposed opposite to the first electrode, a power supply system for supplying high-frequency power to the pair of electrodes, and a combination of the power supply system An equilibrium-unbalance conversion apparatus for plasma generation used in a plasma surface treatment apparatus having a balance-unbalance conversion apparatus to be used and processing the surface of a substrate using generated plasma, and comprising an LC bridge type balance-unbalance conversion The input terminal of the device is used as an input unit, and one end of each of the first and second atmospheric coaxial cables having the same length is connected to the two output terminals of the LC bridge type balun. The first and The other end of each of the two atmospheric coaxial cables is connected to one end of each of the first and second vacuum coaxial cables via the first and second vacuum device coaxial cable connection terminals, respectively. And between the outer conductors at the other end of the first and second vacuum coaxial cables is short-circuited by a short-circuiting conductor having a length of one-third or less of the wavelength of the high-frequency power, and A balance-unbalance converter for high-frequency plasma generation, characterized in that each core wire at the end is used as an output section.

Similarly, in order to achieve the above object, an invention according to claim 8 of the present application is that a vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, and a substrate are set. A pair of electrodes composed of a first electrode and a second electrode disposed opposite to the first electrode, a power supply system for supplying high-frequency power to the pair of electrodes, and a combination of the power supply system 8. A plasma surface treatment apparatus comprising a balance-unbalance conversion device to be used, and processing the surface of a substrate using generated plasma, wherein the balance-unbalance conversion device is according to claim 1. A plasma surface treatment apparatus comprising a balance-unbalance conversion device for high-frequency plasma generation.

Similarly, in order to achieve the above object, the invention according to claim 9 of the present application is that a vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, and a substrate are set. A pair of electrodes composed of a first electrode and a second electrode disposed opposite to the first electrode, a power supply system for supplying high-frequency power to the pair of electrodes, and a combination of the power supply system 8. The plasma surface treatment method comprising the balance-unbalance conversion device used and treating the surface of the substrate using the generated plasma, wherein the balance-unbalance conversion device according to claim 1. The plasma surface treatment is performed by a balance-unbalance converter for high-frequency plasma generation.

According to the balance-unbalance conversion device for high-frequency plasma generation according to claim 1, the main body portion of the balance-unbalance conversion device having the same function as the conventional super-top type balance-unbalance conversion device is placed in the plasma generation vacuum vessel. It is possible to install and apply to the atmosphere side without inserting it into the atmosphere, and adjustment of the length of the balance-unbalance conversion device to accommodate the wavelength of the power used Since the adjustment means can be implemented, and the generation of leakage current at the end of the coaxial cable, which is the cause of abnormal discharge inside the vacuum vessel, can be suppressed, the dimensions of the vacuum vessel are reduced, and Since the uniformity of the plasma between the pair of electrodes is improved, the spatial distribution of the high density plasma using the power source in the VHF band (30 MHz to 300 MHz), which has been regarded as difficult in the past, can be made uniform. That uniform surface treatment, i.e. increase and improving uniformity of the film deposition rate and the etch rate can be reproducibly. This effect greatly contributes not only to the industry of LSIs, LCDs, and photoconductors for copying machines but also to the improvement of productivity in the solar cell industry.

According to the balance-unbalance conversion device for high-frequency plasma generation of claim 2, its value is high as one specific reliable means for realizing claim 1. That is, the main body part of the balance-unbalance conversion device having the same function as the conventional super-type balance-unbalance conversion device should be installed on the atmosphere side without being inserted into the plasma generating vacuum vessel. And adjusting the length of the balance-unbalance conversion device to correspond to the wavelength of the power used, the tube conductor and the cylindrical conductor of the component of the balance-unbalance conversion device installed on the atmosphere side can be adjusted. Since the adjustment of the overlapping length of the joining portion can be easily and easily performed, and the generation of leakage current at the end of the coaxial cable, which is the cause of abnormal discharge inside the vacuum vessel, can be suppressed. Since the size of the container is made compact and the uniformity of the plasma between the pair of electrodes is improved, high density plasma using a power source in the VHF band (30 MHz to 300 MHz), which has been considered difficult in the past, is used. It enables uniform between distribution, uniform surface treatment to the substrate, i.e. improvement and improving uniformity of the film deposition rate and the etch rate can be reproducibly. This effect greatly contributes not only to the industry of LSIs, LCDs, and photoconductors for copying machines but also to the improvement of productivity in the solar cell industry.

According to the balance-unbalance conversion apparatus for high-frequency plasma generation of claim 3, the value is high as one specific reliable means for realizing claim 1. That is, the main body part of the balance-unbalance conversion device having the same function as the conventional super-type balance-unbalance conversion device should be installed on the atmosphere side without being inserted into the plasma generating vacuum vessel. And adjusting the length of the balance-unbalance conversion device to correspond to the wavelength of the power used, the tube conductor and the cylindrical conductor of the component of the balance-unbalance conversion device installed on the atmosphere side can be adjusted. The vacuum vessel can be easily and simply implemented by adjusting the overlapping length of the joining portions, and can suppress the occurrence of leakage current at the end of the coaxial cable that is the cause of abnormal discharge inside the vacuum vessel. Since the size of the plasma is reduced and the uniformity of the plasma between the pair of electrodes is improved, the high-density plasma can be emptied using a power supply in the VHF band (30 MHz to 300 MHz), which has been regarded as difficult in the past. It enables uniform distribution, uniform surface treatment to the substrate, i.e. improvement and improving uniformity of the film deposition rate and the etch rate can be reproducibly. This effect greatly contributes not only to the industry of LSIs, LCDs, and photoconductors for copying machines but also to the improvement of productivity in the solar cell industry.

In addition, the structure of the apparatus of Claim 3 is simple in the structure of the coaxial cable connection terminal for vacuum devices which is one of the structural members compared with the case of the said Claim 2.

According to the balance-unbalance converter for high-frequency plasma generation according to claim 4, there is a problem in applying the conventional half-wavelength bypass type balance-unbalance converter and LC bridge-type balance-unbalance converter to high-frequency plasma generation. The generation of abnormal discharge near the power feeding part due to the leakage current from the end of the coaxial cable inside the vacuum vessel can be reliably suppressed, and the main body of the balance-unbalance conversion device can be used for plasma generation. The length of the balance-unbalance conversion device can be adjusted without adjusting the length of the balance to match the wavelength of the power used without being inserted into the vacuum vessel. Since the dimensions of the vacuum vessel are reduced and the uniformity of plasma between the pair of electrodes is improved, the VHF band (30 MHz to 300 MHz, which has been regarded as difficult in the past). Using the power of Hz) enables uniform spatial distribution of the high-density plasma, uniform surface treatment to the substrate, i.e. improvement and improving uniformity of the film deposition rate and the etch rate can be reproducibly. This effect greatly contributes not only to the industry of LSIs, LCDs, and photoconductors for copying machines but also to the improvement of productivity in the solar cell industry.

According to the balance-unbalance conversion apparatus for high-frequency plasma generation of claim 5, the value is high as one specific reliable means for realizing claim 4. That is, the main body of the balance-unbalance conversion device having the same function as the conventional half-wavelength detour-type balance-unbalance conversion device is installed on the atmosphere side without being inserted into the plasma generating vacuum vessel. The length of the coaxial cable of the component of the balance-unbalance conversion apparatus installed on the atmosphere side can be adjusted and the length of the balance-unbalance conversion apparatus can be adjusted to correspond to the wavelength of the power used. This makes it possible to easily and easily carry out the adjustment and to suppress the occurrence of leakage current at the end of the coaxial cable, which is the cause of abnormal discharge inside the vacuum vessel, thereby reducing the size of the vacuum vessel. In addition, since the uniformity of the plasma between the pair of electrodes is improved, the spatial distribution of the high-density plasma using the power source in the VHF band (30 MHz to 300 MHz), which has been considered difficult in the past, can be made uniform. Becomes, uniform surface treatment to the substrate, i.e. improvement and improving uniformity of the film deposition rate and the etch rate can be reproducibly. This effect greatly contributes not only to the industry of LSIs, LCDs, and photoconductors for copying machines but also to the improvement of productivity in the solar cell industry.

According to the balance-unbalance conversion apparatus for high-frequency plasma generation of claim 6, the value is high as one specific reliable means for realizing claim 4. That is, the main body of the balance-unbalance conversion device having the same function as the conventional half-wavelength detour-type balance-unbalance conversion device is installed on the atmosphere side without being inserted into the plasma generating vacuum vessel. The length of the coaxial cable of the component of the balance-unbalance conversion apparatus installed on the atmosphere side can be adjusted and the length of the balance-unbalance conversion apparatus can be adjusted to correspond to the wavelength of the power used. This makes it possible to easily and easily carry out the adjustment and to suppress the occurrence of leakage current at the end of the coaxial cable, which is the cause of abnormal discharge inside the vacuum vessel, thereby reducing the size of the vacuum vessel. In addition, since the uniformity of the plasma between the pair of electrodes is improved, the spatial distribution of the high-density plasma using the power source in the VHF band (30 MHz to 300 MHz), which has been considered difficult in the past, can be made uniform. Becomes, uniform surface treatment to the substrate, i.e. improvement and improving uniformity of the film deposition rate and the etch rate can be reproducibly. This effect greatly contributes not only to the industry of LSIs, LCDs, and photoconductors for copying machines but also to the improvement of productivity in the solar cell industry.

The apparatus of claim 6 has a simple structure because the number of coaxial cables, which is one of the constituent members, is one less than that of the case of claim 5, but a special-purpose coaxial cable branching device is provided. It is necessary to prepare.

According to the balance-unbalance conversion apparatus for high-frequency plasma generation of claim 7, the value is high as one specific reliable means for realizing claim 4. In other words, the leakage current at the joint between the coaxial cable and the electrode inside the vacuum vessel and the occurrence of abnormal discharge near the joint can be reliably suppressed, which was a problem with the conventional LC bridge type balance-unbalance converter. Since the uniformity of the plasma between the pair of electrodes is improved, the spatial distribution of the high-density plasma using the power source in the VHF band (30 MHz to 300 MHz), which has been regarded as difficult in the past, can be made uniform, and the substrate can be made uniform. It is possible to improve the surface treatment, that is, the film forming speed and the etching speed and the uniformity, with good reproducibility. This effect greatly contributes not only to the industry of LSIs, LCDs, and photoconductors for copying machines but also to the improvement of productivity in the solar cell industry.

According to the plasma surface treatment apparatus of claim 8, a vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, a first electrode on which a substrate is set, and the A balance-unbalance conversion device used in combination with a pair of electrodes composed of a second electrode disposed opposite to the first electrode, a power supply system for supplying high-frequency power to the pair of electrodes, and the power supply system 8. A plasma surface treatment apparatus comprising the generated plasma for treating a surface of a substrate, wherein the balance-unbalance conversion device is the balance-unbalance conversion for high-frequency plasma generation according to any one of claims 1 to 7. By configuring the apparatus, the main body portion of the balance-unbalance conversion apparatus can be substantially installed outside the vacuum vessel, and the balance-unbalance conversion apparatus length corresponding to the wavelength of power used is long. Adjustment or LC bridge type circuit adjustment can be performed easily and easily, and leakage current and abnormal discharge at the joint between the coaxial cable and the electrode installed inside the vacuum vessel can be reliably suppressed. Therefore, the spatial distribution of the high-density plasma using a power source in the VHF band (30 MHz to 300 MHz), which has been regarded as difficult in the past, can be made uniform. The film speed and etching speed can be improved and the uniformity can be improved with good reproducibility. This effect greatly contributes not only to the industry of LSIs, LCDs, and photoconductors for copying machines but also to the improvement of productivity in the solar cell industry.

According to the plasma surface treatment method of claim 9, a vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, a first electrode on which a substrate is set, and the A balance-unbalance conversion device used in combination with a pair of electrodes composed of a second electrode disposed opposite to the first electrode, a power supply system for supplying high-frequency power to the pair of electrodes, and the power supply system 8. A plasma surface treatment method comprising: treating a surface of a substrate using generated plasma, wherein the balance-unbalance conversion device is a balance-unbalance conversion for high-frequency plasma generation according to any one of claims 1 to 7. By configuring the apparatus and performing plasma surface treatment, the main body portion of the balance-unbalance conversion apparatus can be substantially installed outside the vacuum vessel, and is adapted to correspond to the wavelength of power used. The length adjustment of the balance-unbalance conversion device can be easily and easily implemented, and the leakage current and abnormal discharge at the joint between the coaxial cable and the electrode installed inside the vacuum vessel can be reliably suppressed, and a pair of electrodes Since the plasma uniformity during the process is improved, the spatial distribution of the high-density plasma using the power source in the VHF band (30 MHz to 300 MHz), which has been regarded as difficult in the past, can be made uniform, and the surface treatment on the substrate can be made uniform. It is possible to improve the film forming speed and the etching speed and improve the uniformity with good reproducibility. This effect greatly contributes not only to the industry of LSIs, LCDs, and photoconductors for copying machines but also to the improvement of productivity in the solar cell industry.

Hereinafter, a balanced / unbalanced conversion apparatus for high-frequency plasma generation according to an embodiment of the present invention, a plasma surface treatment apparatus and a plasma surface treatment method constituted by the balanced / unbalanced conversion apparatus will be described with reference to the drawings. In the following description, as an example of a plasma surface treatment apparatus and a plasma surface treatment method, an apparatus and method for producing an a-Si thin film necessary for producing a solar cell are described. Is not limited to the apparatus and method of the examples below.

(Example 1)
1 to 3, a balanced / unbalanced conversion apparatus for high-frequency plasma generation according to a first embodiment of the present invention, a plasma surface treatment apparatus (plasma CVD apparatus) and a plasma surface treatment method constituted by the balanced / unbalanced conversion apparatus (Plasma CVD method) will be described.

FIG. 1 is a schematic view showing the entire plasma surface treatment apparatus according to the first embodiment, and FIG. 2 is an explanatory view showing a first specific example 100 of a balance-unbalance conversion apparatus which is one configuration of the plasma surface treatment apparatus of FIG. 3 and FIG. 3 are explanatory views showing the configuration of the connection portion between the tubular conductor and the cylindrical conductor, which are constituent members of the first specific example 100 of the balance-unbalance conversion device of FIG.

First, the configuration of the apparatus will be described. 1 to 3, reference numeral 1 denotes a vacuum vessel. The vacuum vessel 1 is provided with a pair of electrodes for converting a discharge gas, which will be described later, into plasma, that is, a first non-grounded electrode 2 and a second non-grounded electrode 4 incorporating a substrate heater 3 (not shown). The first and second non-grounded electrodes 2 and 4 are fixed to the vacuum vessel 1 by insulator support members 5a and 5b (not shown), respectively. A large number of small holes 6 having a diameter of about 2 mm to 10 mm are arranged in the first non-grounded electrode 2 with an opening ratio of 40% to 60%. An earth shield 7 is disposed around the first non-grounded electrode 2. The earth shield 7 suppresses discharge in unnecessary portions, and discharge gas such as SiH 4 supplied from the discharge gas supply tubes 8a and 8b is disposed in the rectifying hole 9 and the non-ground electrode 2 (not shown). It has a function of supplying uniformly between the pair of electrodes 2 and 4 through a large number of small holes 6. The earth shield 7 is used in combination with the exhaust pipe 10 and a vacuum pump 11 (not shown), and thus has a function of discharging the used discharge gas that has been converted into plasma in the plasma generation space.

The pressure in the vacuum vessel 1 is monitored by a pressure gauge (not shown), and is automatically adjusted and set to a predetermined value by a pressure adjustment valve (not shown). In the case of the present embodiment, when the discharge gas has a flow rate of about 500 sccm to 1500 sccm, the pressure can be adjusted to about 0.01 Torr to 10 Torr (1.33 Pa to 1330 Pa). The vacuum ultimate pressure of the vacuum vessel 101 is about 2 to 3E-7 Torr (2.66 to 3.99E-5 Pa).

Reference numeral 12 denotes a substrate, which is installed on the second non-grounded electrode 4 by opening and closing a gate valve 13 (not shown). Then, it is heated to a predetermined temperature by a substrate heater 3 (not shown).

Reference numeral 14 denotes a high-frequency power source, which generates power having a frequency of 30 MHz to 300 MHz (VHF band). The power is supplied to the coaxial cable 15, the impedance matching unit 16, the second coaxial cable 109b described later, the balance-unbalance conversion device 100 described later, and the first and second feeders surrounded by the insulating rings 102a and 102b (not shown). The power is supplied to the power supply points 17a and 17b of the pair of electrodes 2 and 4 through 18a and 18b.

Reference numeral 100 is a first specific example of the balance-unbalance conversion apparatus and has the configuration shown in FIG. In FIG. 2, a flange 108 disposed on the wall of the vacuum vessel 1, a metal core rod 105 used in combination with the flange 108, a first dielectric 106a, a first tubular conductor 107a, and a second The metal core rod 105 and the first tubular conductor 107a on the vacuum side surface of the coaxial cable connecting terminal 103 for a vacuum device comprising the dielectric 106b, the second tubular conductor 107b, and the third dielectric 106c The core wire 110a and the outer conductor 111a at one end of the first coaxial cable 109a surrounded by the third tubular conductor 107c are connected via a plug 112a and a nut 113a, respectively, and the vacuum One end of the third tubular conductor 107c is connected to the second tubular conductor 107b on the vacuum side surface of the coaxial cable connection terminal 103, and the third tubular conductor is connected. Insulating ring 114a is installed between the external conductor 111a of the body 107c and the first coaxial cable 109a. On the other hand, the metal core rod 105 and the first tube-type conductor 107a on the air side surface of the vacuum coaxial cable connection terminal 103 are surrounded by a fourth tube-type conductor 107d and a cylindrical conductor 115, respectively. A core wire 110b and an outer conductor 111b at one end of the second coaxial cable 109b are connected via a plug 112b and a nut 113b, respectively, and a second tube type on the air side surface of the vacuum coaxial cable connection terminal 103. One end of the fourth tubular conductor 107d is connected to the conductor 107b, and the other end of the fourth tubular conductor 107d and one end of the cylindrical conductor 115 are connected to each other. The cylindrical conductor 115 is in close contact with each other so as to have a relationship between a cylinder and an outer cylinder, and the other end of the cylindrical conductor 115 is in close contact with the outer conductor 111b of the second coaxial cable 109b. Body 107 And cylindrical conductor 115 and the insulating ring 114b between the second coaxial cable outer conductor 111b, 114c are installed. Here, the insulating ring is not necessarily a necessary member, and it is sufficient that the outer conductor of the first coaxial cable 109a and the third tubular conductor 107c are not short-circuited. The distance from the end face of the first coaxial cable 109a to the flange 108 is equal to the distance from the end face of the third tubular conductor 107c to the flange 108, and the third pipe The distance from the other end of the type conductor 107c, that is, the end on the open side to the end face 116 on the closed side of the cylindrical conductor is four wavelengths λ of the high frequency power supplied from the high frequency power source. Set to a fraction. Then, the core wire 110b and the outer conductor 111b at the other end of the second coaxial cable 109b are used as input parts, and the other core wire 110a and the outer conductor 111a of the first coaxial cable 109a are used as output parts. The power supply points 17a and 17b on the electrodes 2 and 4 are connected via the second power supply lines 18a and 18b. The first and second power supply lines 18a and 18b connected to the core wire 110a and the outer conductor 111a of the output unit are covered with insulating rings 102a and 102b (not shown), so that abnormal discharge is suppressed.

However, in the above configuration, the insulating ring 114a installed between the third tubular conductor 107c and the outer conductor 111a of the first coaxial cable 109a is connected to the third tubular conductor 107c and the outer conductor 111a. The first coaxial cable 109a is used to prevent a short circuit with the outer conductor 111a, and is not necessarily essential. Similarly, the insulating rings 114b and 114c installed between the fourth tubular conductor 107d and the cylindrical conductor 115 and the outer conductor 111b of the second coaxial cable are also used to prevent a short circuit. However, it is not always essential.

The distance between the third tubular conductor 107c and the outer conductor 111a of the first coaxial cable 109a is not particularly problematic as long as insulation can be ensured. In order to suppress the conductive state, the Paschen's law is taken into consideration, so that the distance between the pair of electrodes is set to one-fifth to one-tenth, or five times or more.

1 and 2, the circuit in which the end 116 of the cylindrical conductor 115 is viewed from the end face of the first coaxial cable 109a and the open end face of the third tubular conductor 107c has a length of wavelength. Since it is the same as a feeder with a short-circuited tip that is a quarter, the impedance of its propagation path is infinite. Accordingly, current leakage from the end face of the outer conductor 111a of the first coaxial cable 109a does not occur.

In the adjustment of the length of the balance-unbalance conversion device 100 for suppressing the generation of the leakage current, the influence of the first, second, and third insulating rings 114a, 114b, 114c and the second dielectric 106b. The wavelength of the radio wave when propagating through the third tubular conductor 107c, the fourth tubular conductor 107d, and the cylindrical conductor 115 is different from the wavelength when propagating in vacuum, and Since it may be different from the wavelength value obtained by theoretical calculation in advance, it is necessary and important to make simple adjustment while actually supplying power. In this case, it is possible to confirm a desired leakage current suppressing function by sliding the connecting portion of the cylindrical conductor 115 that is in close contact with the fourth tubular conductor 107d. Here, as shown in FIG. 3, by installing a slit 118 in a cylindrical conductor 115 and using a fastening band 119 together, both can be easily slid and adhesion between the two can be ensured. Can be implemented. Then, by using the fastening screw 117 in combination with the end portion 116 of the cylindrical conductor 115 and the connecting portion of the outer conductor of the second coaxial cable 109a, the adhesion between the two can be reliably implemented.

In the adjustment of the length of the balance-unbalance conversion device 100 for suppressing the occurrence of the leakage current, if it is difficult to confirm the leakage current suppression function, a confirmation means as described below can be used. . That is, in FIG. 1, a VSWR meter for measuring a voltage standing wave ratio (abbreviated as VSWR for short) not shown is installed between the impedance matching device 16 and the balun device 100. The ratio of the maximum value and the minimum value of the voltage of the standing wave generated by the interference between the traveling wave and the reflected wave when the connecting portion of the cylindrical conductor 115 is slid (here, this is expressed as S). Measure and display. Then, it is generated by a traveling wave propagating from the output side of the impedance matching unit 16 to the pair of electrodes via the balance-unbalance conversion device 100 and a reflected wave returning from the pair of electrodes side to the impedance matching unit 16. Information on the voltage maximum value and voltage minimum value of the standing wave is read as the value of S (ie, VSWR). If S = 3 or more, the length adjustment of the second specific example 100 of the balance-unbalance conversion apparatus is adjusted. Generally, if there is no abnormality in the joint portion of the coaxial cable, the above S is about S = 3 or less.

Next, a method of forming a-Si for an a-Si solar cell using the plasma surface treatment apparatus having the above configuration will be described. 1 to 3, in advance, the substrate 12 is placed on the second non-grounded electrode 4 and the vacuum pump 11 is operated to remove impurity gas and the like in the vacuum vessel 1, and then the discharge gas supply pipe 8a. , 8b, while supplying SiH4 gas at a pressure of, for example, 500 sccm and a pressure of 0.5 Torr (66.5 Pa), high-frequency power, for example, power of a frequency of 60 MHz, for example, 500 W is supplied to the pair of electrodes 2, 4. The substrate temperature is kept in the range of 80 to 350 ° C., for example, 180 ° C.

That is, the output of the high-frequency power supply 14 is set to 500 W at 60 MHz, for example, and the output is covered with the balanced / unbalanced conversion device 100 including the coaxial cable 15, the impedance matching device 16, and the second coaxial cable 109b, and insulating rings 102a and 102b (not shown). The power supply points 17a and 17b are supplied via the first and second power supply lines 18a and 18b. In this case, by using a combination of the traveling wave and reflected wave power value monitors attached to the impedance matching unit 16 and the high frequency power source 14, the reflected wave of the supplied power does not return to the upstream side of the impedance matching unit 16. Can be. If the adjustment of the length of the first specific example 100 of the balance-unbalance conversion device is not matched to the frequency of 60 MHz, the current between the first coaxial cable 109a and the pair of electrodes 2, 4 Is generated, the plasma generation is temporarily interrupted, and the length of the first specific example 100 of the balance-unbalance conversion device is adjusted. As shown in FIGS. 2 and 3, the adjustment is performed by loosening the tightening band 119 and the tightening screw 117 of the cylindrical conductor 115 with the slit 118 and closely contacting the fourth tubular conductor 107d. The connecting portion of the cylindrical conductor 115 is slid by an appropriate length. Thereafter, by tightening the tightening band 119 and the tightening screw 117, adhesion between the two can be reliably performed. Then, plasma can be generated again, and it can be confirmed that the reflection of the power is suppressed. As a result, plasma of SiH 4 gas is generated.

If the impedance matching unit 16 and the power value monitor of the traveling wave and the reflected wave cannot adjust the length of the first specific example 100 of the balance-unbalance conversion device, it is ensured by using the VSWR meter. Can be implemented.

Since the power supply to the power supply points 17a and 17b can be performed while suppressing the occurrence of leakage current, abnormal discharge such as local discharge does not occur in the vicinity of the first and second power supply lines 101a and 101b. The insulating effect of the insulating rings 102a and 102b around the first and second power supply lines 18a and 18b also suppresses abnormal discharge between them. In addition, in the prior art, since leakage current related to the ground structure and wiring situation around the pair of electrodes is generated, it is difficult to generate plasma with good reproducibility. A good plasma can be generated.

In the above process, when SiH 4 gas is turned into plasma, radicals such as SiH 3, SiH 2, and SiH existing in the plasma are diffused by a diffusion phenomenon and adsorbed on the surface of the substrate 12, thereby depositing an a-Si film. To do. It is a well-known technique that microcrystalline Si, thin film polycrystalline Si, or the like can be formed by optimizing the flow ratio, pressure, and power of SiH4 and H2 in the film forming conditions.

Specific conditions in the case of film formation by the above procedure will be described below. A-Si having a film forming speed of 1 nm / s and a film thickness distribution of ± 10% is formed on a glass substrate 12 having a size of about 1200 mm × 300 mm (thickness 4 mm).

The film forming conditions are as follows.
(Film forming conditions)
Discharge gas: SiH4
Flow rate: 500sccm
Pressure: 0.5 Torr (66.5 Pa)
Power supply frequency: 60 MHz
Power: 500W
The temperature of the substrate 13: 180 ° C.

  When the plasma is generated under the film forming conditions, the balance-unbalance conversion device 100 matches the transmission characteristics at the connection portion between the power supply system and the pair of electrodes, and the generation of leakage current is suppressed. The spatial distribution of plasma density is uniform with good reproducibility compared to the conventional case. As a result, the film thickness distribution of the a-Si film to be formed becomes uniform with good reproducibility compared to the conventional case. Numerically, film formation is possible when the a-Si film thickness distribution is within ± 10.

In this embodiment, since the feeding point is set to one point (a pair) for each of the pair of electrodes 2 and 4, the substrate size is limited to about 1200 mm × 300 mm. However, if the number of feeding points is increased, the width of the size is increased. It is natural that it can be expanded.

Further, in the manufacture of a-Si solar cells, thin film transistors, and photosensitive drums, there is no problem in performance as long as the film thickness distribution is within ± 10%. According to the above embodiment, it is possible to obtain a significantly better film thickness distribution as compared with the conventional apparatus and method even when a power supply frequency of 60 MHz is used. This means that the industrial value related to productivity improvement and cost reduction in the manufacturing field of a-Si solar cells, thin film transistors, and photosensitive drums is remarkably large.

(Example 2)
With reference to FIG. 1 and FIG. 4, a balanced / unbalanced conversion apparatus for high-frequency plasma generation according to a second embodiment of the present invention, a plasma surface treatment apparatus (plasma CVD apparatus) and a plasma surface treatment method constituted by the balanced / unbalanced conversion apparatus (Plasma CVD method)
Will be described.

First, the configuration of the apparatus will be described. However, the same members as those shown in FIG. 1 to FIG. FIG. 4 is an explanatory view showing a second specific example of a balance-unbalance conversion apparatus which is one configuration of the plasma surface treatment apparatus according to the second embodiment. The configuration of the plasma surface treatment apparatus of the second embodiment shown in FIG. 4 is replaced with the first specific example 100 of the balance / unbalance conversion apparatus used as the balance / unbalance conversion apparatus in the configuration of the first embodiment, that is, FIG. The second specific example 200 of the balance-unbalance conversion device shown in FIG. 4 is used, and other device components are the same. Therefore, the constituent elements of the apparatus other than the second specific example 200 of the balance-unbalance conversion apparatus will be described with reference to FIGS. 1 to 3, and description thereof will be omitted here. Further, the procedure for performing the plasma surface treatment using the second specific example 200 of the balance-unbalance conversion apparatus is omitted, and the first embodiment is referred to.

FIG. 4 is a diagram illustrating the configuration of a second specific example 200 of the balance-unbalance conversion apparatus used in place of the first specific example 100 of the balance-unbalance conversion apparatus, which is one configuration of the plasma surface treatment apparatus shown in FIG. FIG.

The configuration of the second specific example 200 of the balance-unbalance conversion apparatus shown in FIG. 4 is as follows. A flange 202 disposed on the wall of the vacuum vessel 1, a metal core rod 105 used in combination with the flange 202, a first dielectric 106 a, a first tubular conductor 107 a, and a second dielectric 106 b The metallic core rod 105 and the first tubular conductor 107a on the vacuum side surface of the coaxial cable connecting terminal 201 for a vacuum device comprising the second tubular conductor 203 which is in close contact with the flange 202, respectively, The core wire 110a and the outer conductor 111a at one end of the first coaxial cable 109a surrounded by the second tube-type conductor 203 are connected via a plug 112a and a nut 113a, and the second tube An insulating ring 114a is installed between the type conductor 203 and the outer conductor 111a of the first vacuum coaxial cable 109a. On the other hand, the metal core rod 105 and the first tubular conductor 107a on the atmospheric side of the coaxial cable connection terminal 201 for the vacuum apparatus are surrounded by the second tubular conductor 203 and the cylindrical conductor 115, respectively. The core wire 110b and the outer conductor 111b at one end of the second coaxial cable 109b are connected via a plug 112b and a nut 113b, and the other end of the second tubular conductor 203 and the cylinder are connected. The open end of the type conductor 115 is brought into close contact with the inner cylinder and the outer cylinder, and the central portion of the bottom surface 116 of the cylindrical conductor 115 is connected to the outer conductor 111b of the second coaxial cable 109b. In addition, the insulating rings 114b and 114c are installed between the second tubular conductor 203 and the cylindrical conductor 115 and the outer conductor 111b of the first atmospheric coaxial cable 109b. Here, the insulating ring is not necessarily a necessary member, and the second tube-type conductive material is used so that the external conductor 111a of the first coaxial cable and the second tube-type conductor 203 are not short-circuited. It is sufficient that the body 203 and the cylindrical conductor 115 and the outer conductor 111b of the second coaxial cable 109b are not short-circuited. The distance from the end surface of the first coaxial cable 109a to the flange 202 is set equal to the distance from the end surface of the second tubular conductor 203 to the flange 202, and the first The distance from the open end surface of the second tubular conductor 203 to the bottom surface 116 of the cylindrical conductor 115 is set to a quarter of the wavelength of the high frequency power supplied from the high frequency power source. Then, the core wire 110b and the outer conductor 111b at the other end of the second coaxial cable 109b are used as input portions, and the other core wire 110a and the outer conductor 111a of the first coaxial cable 109a are used as output portions. The power supply points 17a and 17b on the electrodes 2 and 4 are connected via the first and second power supply lines 18a and 18b. The first and second power supply lines 18a and 18b are covered with insulating rings 102a and 102b (not shown).

However, in the above configuration, the insulating ring 114a installed between the second tubular conductor 203 and the outer conductor 111a of the first vacuum coaxial cable 109a is provided with the second tubular conductor 203. And the outer conductor 111a of the first vacuum coaxial cable 109a, and is not necessarily essential. Similarly, the insulating rings 114b and 114c installed between the second tubular conductor 203 and the cylindrical conductor 115 and the outer conductor 111b of the first atmospheric coaxial cable 109b are also indispensable for the same reason. Is not.

The distance between the second tubular conductor 203 and the outer conductor 111a of the first coaxial cable 109a is not particularly limited as long as insulation can be ensured, but preferably, the influence of electrons and ions during plasma generation. In order to suppress the conductive state, the Paschen's law is taken into consideration, so that the distance between the pair of electrodes is set to one-fifth, one-fifth, or five times or more.

1 and 4, the circuit in which the end portion 116 of the cylindrical conductor 115 is viewed from the end face of the first coaxial cable 109a and the open end face of the second tubular conductor 203 has a length of wavelength. Since it is the same as a short-circuit feeder, which is a quarter, the impedance of its propagation path is infinite. Therefore, current leakage from the end face of the outer conductor 111a of the first coaxial cable 109a does not occur.

In adjusting the length of the balance-unbalance conversion device 200 for suppressing the generation of the leakage current, the first, second, and third insulating rings 114a, 114b, 114c and the second dielectric 106b are affected. The wavelength of the radio wave when propagating through the second tubular conductor 203 and the cylindrical conductor 115 is different from the wavelength when propagating in vacuum, and the wavelength value obtained by theoretical calculation in advance. Therefore, it is necessary and important to simply adjust while actually supplying power. In this case, it is possible to confirm a desired leakage current suppressing function by sliding the connecting portion of the cylindrical conductor 115 that is in close contact with the second tubular conductor 203. Here, as shown in FIG. 3, the slit 118 is installed in the cylindrical conductor 115 and the fastening band 119 is used in combination so that both can be easily slid and the adhesion between the two is ensured. Can be implemented. Then, by using the fastening screw 117 in combination with the end portion 116 of the cylindrical conductor 115 and the connecting portion of the outer conductor of the second coaxial cable 109a, the adhesion between the two can be reliably implemented.

In the adjustment of the length of the balance-unbalance conversion device 200 for suppressing the occurrence of the leakage current, if it is difficult to confirm the leakage current suppression function, a confirmation means as described below can be used. . That is, in FIG. 1, a VSWR meter for measuring a voltage standing wave ratio (abbreviated as VSWR for short) not shown is installed between the impedance matching device 16 and the balun device 200. The ratio of the maximum value and the minimum value of the voltage of the standing wave generated by the interference between the traveling wave and the reflected wave when the connecting portion of the cylindrical conductor 115 is slid (herein, this is expressed as S). Measure and display. Then, it is generated by a traveling wave propagating from the output side of the impedance matching unit 16 to the pair of electrodes via the balance-unbalance conversion device 200 and a reflected wave returning from the pair of electrodes side to the impedance matching unit 16. Information on the voltage maximum value and voltage minimum value of the standing wave is read as the value of S (ie, VSWR). If S = about 3 or more, the length adjustment of the second specific example 200 of the balance-unbalance conversion apparatus is adjusted. Generally, if there is no abnormality in the joint portion of the coaxial cable, the above S is about S = 3 or less.

In the second embodiment, the execution procedure of the plasma surface treatment using the second specific example 200 of the balance-unbalance conversion apparatus is omitted and the first embodiment is referred to. However, as in the first embodiment, Since each of the pair of electrodes 2 and 4 has one feeding point (a pair), the substrate size is limited to about 1200 mm × 300 mm. However, it goes without saying that the size range can be expanded by increasing the number of feeding points.

Moreover, according to the said Example 2, it is possible to obtain a remarkably favorable film thickness distribution compared with the conventional apparatus and method in power supply frequency 30MHz-100MHz. This means that the industrial value related to productivity improvement and cost reduction in the manufacturing field of a-Si solar cells, thin film transistors, and photosensitive drums is remarkably large.

(Example 3)
Referring to FIGS. 5 and 6, a balanced / unbalanced conversion apparatus for high-frequency plasma generation according to a third embodiment of the present invention, a plasma surface treatment apparatus (plasma CVD apparatus) and a plasma surface treatment method constituted by the balanced / unbalanced conversion apparatus. (Plasma CVD method) will be described. First, the configuration of the apparatus will be described. FIG. 5 is a configuration diagram of a plasma surface treatment apparatus according to the third embodiment, and FIGS. 6A and 6B are explanatory diagrams showing an ideal configuration of the third embodiment.

First, the configuration of the apparatus will be described. However, the same members as those shown in FIG. 1 to FIG. The configuration of the plasma surface treatment apparatus of Example 3 shown in FIG. 5 is the same as that of FIG. 1 except for the power supply system described below. That is, the high-frequency power source 14, the atmospheric coaxial cable 15, the impedance matching unit 16, the first atmospheric coaxial cable 501, the LC bridge type balance-unbalance conversion device 502, the second and third atmospheric coaxial cables 503a, 503b, First and second vacuum coaxial cable connection terminals 504a and 504b, first and second vacuum coaxial cables 505a and 505b, a short-circuiting conductor 506, and first and second feeders 18a disposed in the vacuum vessel. , 18b, except for the power supply system. Therefore, the configuration of the apparatus other than the power supply system will be described with reference to FIG. 1, and description thereof will be omitted here. Further, the procedure for performing the plasma surface treatment of the third embodiment using the power supply system is omitted, and the first embodiment is referred to.

In the above configuration, the reason why the shorting conductor 506 is used as means for short-circuiting the outer conductors of the first and second vacuum coaxial cables 505a and 505b is as follows. That is, as a basic configuration of the third embodiment, as shown in FIG. 5, a vacuum vessel 1 having an exhaust system and discharge gas supply pipes 8a and 8b for supplying a discharge gas into the vacuum vessel 1 are provided. A pair of electrodes composed of a first electrode 4 on which the substrate 12 is set and a second electrode 2 placed opposite to the first electrode 4, and a power supply system for supplying high-frequency power to the pair of electrodes 14, 15, 16, 501 and a balance-unbalance conversion device 502 used in combination with the power supply system are arranged, and the core wires at one end of each of two coaxial cables 505 a, 505 b having the same length Are connected to power supply points 17a and 17b provided on the pair of electrodes, the outer conductors of the respective coaxial cables at the ends are short-circuited, and the other ends of the two coaxial cables 505a and 505b are connected. Core wire and The unit conductor is provided with means 502 for supplying electric power via coaxial cable connection terminals 504a and 504b arranged on the wall of the vacuum vessel 1 and adjusting the phase difference of the voltage of the electric power to 180 degrees. It is a feature.

As an action of short-circuiting the outer conductor at one end of each of the two coaxial cables 505a and 505b having the same length, first, the respective end portions of the two coaxial cables 505a and 505b are used. The leakage currents generated in are equal in magnitude and opposite in direction, so they are erased from each other. As a result, the phase difference of 180 degrees from the respective core wires of the two coaxial cables 505a and 505b, which are output portions, is obtained. Electric power having a voltage can be supplied while suppressing leakage current. Second, since the potentials of the outer surfaces of the outer conductors at the ends of the two coaxial cables 505a and 505b are the same, the reference value of the voltage of the power output from the core wires of the two coaxial cables 505a and 505b Is stable over time. This means that the degree to which the two coaxial cables 505a and 505b wired inside the vacuum vessel are affected by the structure of the members inside the vacuum device and the grounding condition is significantly reduced.

As means for short-circuiting the ends of the two coaxial cables 505a and 505b, as shown in FIG. 6A, two coaxial cables 311a and 311b are arranged in parallel inside the vacuum vessel, It is common sense and ideal to create a short circuit state 312 by closely contacting the conductors. In this state, the currents leaking to the outer conductors of the two coaxial cables 311a and 311b are canceled each other, and the leakage current can be reliably prevented. However, the configuration including the coaxial cables 314a and 314b for the atmosphere shown in FIG. 6A, the coaxial cable connection terminal 315 for the vacuum apparatus, the core wires 317a and 317b of the vacuum coaxial cables 311a and 311b, etc. If 315 is not a general-purpose member but has a special specification, and if the vacuum coaxial cables 311a and 311b are in close contact in parallel, the usage conditions may be restricted when actually applied. Therefore, it is considered that the configuration of FIG. 6A is practically limited to the application of a special case. Further, as shown in FIG. 6B, this is a configuration example including vacuum coaxial cables 321a and 321b including atmospheric coaxial cables 324a and 324b, vacuum device coaxial cable connection terminals 325a and 325b, and core wires 327a and 327b. The vacuum device coaxial cable connection terminals 325a and 325b are general-purpose members, and are inexpensive and convenient for application, but the state 322 of connection in the form of dots is unstable. Therefore, it is considered that this configuration is practically limited to special case applications.

Therefore, in practice, the short-circuit means for the outer conductor at the end of the coaxial cable shown in FIG. Of course, the configuration as shown in FIGS. 6A and 6B is the most preferable mode.

In FIG. 5, the output of the high frequency power source 14, for example, the power of 500 W at a frequency of 70 MHz, is supplied to the LC bridge type unbalanced converter 502 through the atmospheric coaxial cable 15, the impedance matching device 16, and the first atmospheric coaxial cable 501. Is input. The power input to the LC bridge type balun device 502 is divided into two, and the voltage phase difference between the two distributed powers is adjusted to 180 degrees. The two distributed powers having a phase difference of 180 degrees in the voltage propagate through the second and third atmospheric coaxial cables 503a and 503b having the same length, for example, a length of 60 cm, for example. And the second vacuum device coaxial cable connection terminals 504a and 504b, the lengths of which are the same, for example, 20 cm in length, and the outer conductors at one end are short-circuited by the short-circuiting conductor 506. The first and second vacuum coaxial cables 505a and 505b are transmitted. The power transmitted to the first and second vacuum coaxial cables 505a and 505b is supplied to the power feed points 17a and 17b using the first and second feed lines 18a and 18b connected to the core wires at the ends thereof. To be supplied.

  Here, the length of the short-circuiting conductor 506 is set to be not more than one-third of the wavelength of the power used, and preferably not more than one-sixth. The reason for setting the length of the short-circuiting conductor 506 to not more than one-third of the wavelength of the power, preferably to not more than six-thousand is due to the skin effect at the time of power propagation that appears prominently at ultra-high frequencies. This is because the short-circuiting conductor 506 cannot exhibit a short-circuiting function due to an increase in impedance. That is, if the length is inappropriate, it means that the two are not short-circuited in an ultrahigh frequency. As a result, the high-frequency power input to the LC bridge type balance-unbalance conversion device 502 via the first atmospheric coaxial cable 501 is one of the first and second vacuum coaxial cables 505a and 505b serving as an output unit. Electric power having a voltage phase difference of 180 degrees is supplied to the power supply points 17a and 17b through the first and second feeders 18a and 18b.

However, in the above power supply system, one end of each of the first and second vacuum coaxial cables 505a and 505b has a length of one-third or less, preferably six-tenths of the wavelength of the power. If the short-circuiting conductor 506 that is less than or equal to 1 is not short-circuited, a leakage current is present in the vicinity of the outer conductor and the end of each of the first and second vacuum coaxial cables 505a and 505b of the output section. Causes a strong abnormal discharge.

That is, the length between the outer conductors at one end of the first and second vacuum coaxial cables 505a and 505b is not more than one third of the wavelength of the power, preferably not more than sixteenth. It can be said that the means for short-circuiting with the short-circuiting conductor 606 is epoch-making.

In the third embodiment, the procedure for performing the plasma surface treatment using the apparatus shown in FIG. 5 is omitted and reference is made to the first embodiment. Since each feeding point is one point (a pair), the substrate size is limited to about 1200 mm × 300 mm. However, it goes without saying that the size range can be expanded by increasing the number of feeding points.

Moreover, according to the said Example 3, it is possible to obtain a remarkably favorable film thickness distribution compared with the conventional apparatus and method in power supply frequency 30MHz-100MHz. This means that the industrial value related to productivity improvement and cost reduction in the manufacturing field of a-Si solar cells, thin film transistors, and photosensitive drums is remarkably large.

Example 4
7 and 8, a balanced / unbalanced conversion apparatus for high-frequency plasma generation according to a fourth embodiment of the present invention, a plasma surface treatment apparatus (plasma CVD apparatus) and a plasma surface treatment method constituted by the balanced / unbalanced conversion apparatus. (Plasma CVD method) will be described. First, the configuration of the apparatus will be described. However, the same members as those shown in FIG. 1 to FIG. FIG. 7 is a schematic view showing the entire plasma surface treatment apparatus according to the fourth embodiment, and FIG. 8 is an explanatory view showing a fourth specific example 300 of the balance-unbalance conversion apparatus which is one configuration of the plasma surface treatment apparatus of FIG. It is.

The configuration of the plasma surface treatment apparatus according to the fourth embodiment shown in FIGS. 7 and 8 is the same as that of the first embodiment 100 of the balance / unbalance apparatus used as the balance / unbalance apparatus in FIG. Instead, the fourth specific example 300 of the balance-unbalance conversion apparatus shown in FIG. 8 is used, and other apparatus components are the same. Therefore, the constituent elements of the apparatus other than the fourth specific example 300 of the balance-unbalance conversion apparatus will be described with reference to FIG.

7 and 8, among the first and second vacuum device coaxial cable connection terminals 303a and 303b arranged on the wall of the vacuum vessel 1, on the atmosphere side surface of the first vacuum device coaxial cable connection terminal 303a. One end of a third coaxial cable 305 having a length L, for example, 30 cm, is connected, and the other end of the second coaxial cable 305 is connected to the first connection portion of the T-connector 307 for the coaxial cable. The length of the second connection portion of the T-connector 307 for the coaxial cable is 137 cm (the frequency is 70 MHz, the wavelength is 4.2 m in vacuum, the wavelength when propagating the coaxial cable, for example, one half of the wavelength λ of the high-frequency power. The second coaxial cable 3 having a length equal to a value obtained by adding the length L (for example, 30 cm) of the third coaxial cable, ie, (λ / 2 + L), for example, 167 cm. 06 is connected, and the other end of the second coaxial cable 306 is connected to the atmospheric side surface of the second coaxial cable connection terminal 303b for the vacuum device disposed on the wall of the vacuum vessel 1. One end portion of the first coaxial cable 304 is connected to the third connection portion of the T-connector 307 for the coaxial cable. The core wire and the outer conductor at the other end of the first coaxial cable 304 are used as the input unit. The first and second vacuum coaxial cables 302a and 302b having the same length, for example, 20 cm, are respectively formed on the vacuum side surfaces of the first and second vacuum device coaxial cable connection terminals 303a and 303b. One end is connected, and each outer conductor of the other end of each of the first and second vacuum coaxial cables 302a and 302b has a length of one third or less of the wavelength of the power used, preferably The first and second feeders 18a are short-circuited by a short-circuiting conductor 308 having a thickness of less than 1/6, for example, 5 cm (70 MHz, λ = 4.2 m), and the core wires 301a and 301b are used as output portions. , 18b. In this case, the voltage and current output from the core wires 301a and 301b are the wavelength of the power used by the length of the two transmission lines branched at the connection between the first coaxial cable 304 and the coaxial cable T-connector 307. Therefore, the phase difference is 180 degrees, which is a balanced transmission line. That is, the balance-unbalance conversion apparatus 300 has the core wire and the outer conductor at one end of the first coaxial cable 304 as input parts and the core wires 301a and 301b of the first and second vacuum coaxial cables as output parts. It is configured.

Here, the lengths of the first and second vacuum coaxial cables 302a and 302b need to be the same. Further, the length of the short-circuiting conductor 308 that short-circuits the ends of the coaxial cables 302a and 302b needs to be shortened to one-third or less of the wavelength of the power used, preferably to about one-sixth or less. is there. This is because the short-circuiting conductor 308 cannot exhibit the short-circuiting function due to an increase in impedance due to the skin effect during power propagation that appears prominently at high frequencies. That is, if the length is inappropriate, the potential is generated in the length direction of the short-circuiting conductor 308 without short-circuiting the both, and as a result, leakage current is generated from the ends of the coaxial cables 302a and 302b. An abnormal discharge occurs due to. That is, it is an important point for suppressing leakage current that the outer conductors at the ends of the first and second vacuum coaxial cables 302a and 302b are at the same potential, that is, short-circuited.

That is, the length between the outer conductors at one end of the first and second vacuum coaxial cables 302a and 302b is not more than one third of the wavelength of the power, preferably not more than sixteenth. It can be said that the means for short-circuiting with the short-circuiting conductor 308 is epoch-making.

Next, a method of forming a-Si for an a-Si solar cell using the surface treatment apparatus having the above configuration will be described. 7 and 8, the substrate 12 is previously placed on the second non-grounded electrode 4, the vacuum pump 11 is operated, and the impurity gas in the vacuum vessel 1 is removed, and then the discharge gas supply pipe 8a. While supplying SiH4 gas from 8b at, for example, 500 sccm and a pressure of 0.5 Torr (66.5 Pa), high-frequency power is supplied to the pair of electrodes 2 and 4, for example, power of 500 W at a frequency of 70 MHz. The substrate temperature is kept in the range of 80 to 350 ° C., for example, 180 ° C.

That is, the output of the high-frequency power source 14 is, for example, 70 MHz, the output of 500 W is supplied through the coaxial cable 15 and the impedance matching unit 16, and the specific example 300 of the balance-unbalance conversion device including the first coaxial cable 304 and the insulating ring 102a (not shown). , 102b is supplied to the power feeding points 17a and 17b via the first and second feeding lines 18a and 18b. In this case, the reflected wave of the supplied power can be prevented from returning to the upstream side of the impedance matching unit 16 by adjusting the impedance matching unit 16. If the length adjustment of the third specific example 300 of the balance-unbalance conversion device is not matched to the frequency of 70 MHz, the end portions of the first and second vacuum coaxial cables 302a and 302b When the leakage current is generated, the generation of plasma is temporarily stopped, and the length of the second coaxial cable 306 of the constituent member of the third specific example 300 of the balance-unbalance conversion apparatus is changed. In that case, several second coaxial cables 306 having different lengths are prepared in advance, and are sequentially exchanged to generate plasma again to confirm that the reflection of the power is suppressed. Can do. As a result, plasma of SiH 4 gas is generated. If the presence or absence of leakage current cannot be confirmed only by the degree of power reflection, the VSWR meter is connected to the impedance matching device 16 and the coaxial cable T-type connector 307 as in the first and second embodiments. It is installed in between to measure and display the ratio between the maximum value and the minimum value of the voltage of the standing wave generated by the interference between the traveling wave and the reflected wave (here, this is expressed as S). Then, it is generated by a traveling wave propagating from the output side of the impedance matching unit 16 to the pair of electrodes via the balance-unbalance conversion device 300 and a reflected wave returning from the pair of electrodes side to the impedance matching unit 16. Information on the voltage maximum value and voltage minimum value of the standing wave is read as the value of S (ie, VSWR). If S = about 3 or more, the length adjustment of the second specific example 200 of the balance-unbalance conversion apparatus is adjusted. Generally, if there is no abnormality in the joint portion of the coaxial cable, the above S is about S = 3 or less.

It should be noted that the preparation of the second coaxial cable 306 of the fourth specific example 300 of the balance-unbalance conversion device having several different lengths in advance means that the frequency of the high-frequency power source 14 is slightly changed. The advantage is that it can be handled by replacing the cable 306.

When the SiH 4 gas is turned into plasma, radicals such as SiH 3, SiH 2, and SiH existing in the plasma diffuse due to a diffusion phenomenon and are adsorbed on the surface of the substrate 12, thereby depositing an a-Si film. It is a well-known technique that microcrystalline Si, thin film polycrystalline Si, or the like can be formed by optimizing the flow ratio, pressure, and power of SiH4 and H2 in the film forming conditions.

Specific conditions in the case of film formation by the above procedure will be described below. A-Si having a film forming speed of 1 nm / s and a film thickness distribution of ± 10% is formed on a glass substrate 12 having a size of about 1200 mm × 300 mm (thickness 4 mm).

The film forming conditions are as follows.
(Film forming conditions)
Discharge gas: SiH4
Flow rate: 500sccm
Pressure: 0.5 Torr (66.5 Pa)
Power supply frequency: 70 MHz
Power: 500W
The temperature of the substrate 13: 180 ° C.

When plasma is generated under the above-mentioned film forming conditions, the transmission characteristics at the connection between the power supply system and the pair of electrodes are matched by the balance-unbalance converter as in the first to third embodiments, and the leakage current is reduced. Since the generation is suppressed, the spatial distribution of the density of the generated plasma becomes uniform with good reproducibility compared to the conventional case. As a result, the film thickness distribution of the a-Si film to be formed becomes uniform with good reproducibility compared to the conventional case. Numerically, film formation is possible when the a-Si film thickness distribution is within ± 10.

In the fourth embodiment, since the feeding point is set to one point (a pair) for each of the pair of electrodes 2 and 4, the substrate size is limited to about 1200 mm × 300 mm. However, if the number of feeding points is increased, the width of the size is increased. Of course, it is expandable.

Further, in the manufacture of a-Si solar cells, thin film transistors, and photosensitive drums, there is no problem in performance as long as the film thickness distribution is within ± 10%. According to the above embodiment, it is possible to obtain a significantly better film thickness distribution as compared with the conventional apparatus and method even when a power supply frequency of 70 MHz is used. This means that the industrial value related to productivity improvement and cost reduction in the manufacturing field of a-Si solar cells, thin film transistors, and photosensitive drums is remarkably large.

(Example 5)
With reference to FIGS. 7 and 9, a balanced / unbalanced conversion apparatus for high-frequency plasma generation according to a fifth embodiment of the present invention, a plasma surface processing apparatus (plasma CVD apparatus) and a plasma surface processing method constituted by the balanced / unbalanced conversion apparatus (Plasma CVD method)
Will be described. FIG. 9 is an explanatory view showing a fifth specific example of the balance-unbalance conversion apparatus which is one configuration of the plasma surface treatment apparatus according to the fifth embodiment.

First, the configuration of the apparatus will be described. However, the same members as those shown in FIG. 1 to FIG. The configuration of the plasma surface treatment apparatus of the fifth embodiment shown in FIG. 9 is replaced with the fourth embodiment 300 of the balance / unbalance conversion apparatus used as the balance / unbalance apparatus in the configuration of the fourth embodiment, ie, FIG. The fifth specific example 400 of the balance-unbalance conversion apparatus shown in FIG. 9 is used, and other apparatus components are the same. Therefore, the components of the apparatus other than the fifth specific example 400 of the balance-unbalance conversion apparatus will be described with reference to FIGS. 1 to 8, and description thereof will be omitted here. Further, the procedure for performing the plasma surface treatment using the fifth specific example 400 of the balance-unbalance conversion apparatus is omitted, and the first and fourth embodiments are referred to.

FIG. 9 is an explanatory view showing a fifth specific example 400 of the balance-unbalance conversion apparatus which is one configuration of the plasma surface treatment apparatus of FIG. In FIG. 9, one of the first and second vacuum device coaxial cable connection terminals 303a and 303b disposed on the wall of the vacuum vessel 1 is connected to the atmospheric side of the first vacuum device coaxial cable connection terminal 303a. The first connection portion of the T-type connector 401 is connected, and one end portion of the first coaxial cable 304 is connected to the second connection portion of the T-type connector 401 for the coaxial cable. One end portion of the second coaxial cable 402 whose length is one-half of the wavelength λ of the power used is connected to the third connection portion 401, and the other end portion of the second coaxial cable 402 is connected to the third connection portion 401. Is connected to the atmospheric side surface of the second coaxial cable connecting terminal 303b for the vacuum device disposed on the wall of the vacuum vessel 1. The core wire and the outer conductor at the other end of the first coaxial cable 304 are used as the input unit. The first and second vacuum coaxial cables 302a and 302b having the same length, for example, 20 cm, are respectively formed on the vacuum side surfaces of the first and second vacuum device coaxial cable connection terminals 303a and 303b. One end is connected, and the length between the outer conductors of the other ends of the first and second vacuum coaxial cables 302a and 302b is not more than one third of the wavelength of the power used, preferably Is short-circuited by a short-circuiting conductor 308 of 6/10 or less, for example, 5 cm (70 MHz, λ = 4.2 m), and each of the core wires 301a and 301b is used as an output unit, and the first and second feeder lines Connect to 18a, 18b. In this case, the electric power output from the core wires 301a and 301b is transmitted from the coaxial cable T-type connector 401 to a line composed of the second coaxial cable 402 and the second vacuum coaxial cable 302b, and the coaxial cable, respectively. Propagation from the T-type connector 401 via the line of the second vacuum coaxial cable 302b results in a phase difference of 180 degrees between the two. In other words, the above-described balanced structure in which the core wire and the outer conductor at the other end of the first coaxial cable 304 are used as an input portion, and the core wires 301a and 301b of the first and second vacuum coaxial cables 302a and 302b are used as output portions. The fourth specific example 400 of the unbalance conversion device has a function of balanced transmission (balanced line).

Here, the lengths of the first and second vacuum coaxial cables 302a and 302b need to be the same. Further, the length of the short-circuiting conductor 308 that short-circuits the ends of the coaxial cables 302a and 302b needs to be shortened to one-third or less of the wavelength of the power used, preferably to about one-sixth or less. is there. This is because the short-circuiting conductor 308 cannot exhibit the short-circuiting function due to an increase in impedance due to the skin effect during power propagation that appears prominently at high frequencies. That is, if the length is inappropriate, the potential is generated in the length direction of the short-circuiting conductor 308 without short-circuiting the both, and as a result, leakage current is generated from the ends of the coaxial cables 302a and 302b. An abnormal discharge occurs due to. That is, it is an important point for suppressing leakage current that the outer conductors at the ends of the first and second vacuum coaxial cables 302a and 302b are at the same potential, that is, short-circuited.

That is, the length between the outer conductors at one end of the first and second vacuum coaxial cables 302a and 302b is not more than one third of the wavelength of the power, preferably not more than sixteenth. It can be said that the means for short-circuiting with the short-circuiting conductor 606 is epoch-making.

In the fifth embodiment, the procedure for performing the plasma surface treatment using the fifth specific example 400 of the balance / unbalance conversion apparatus is omitted, and the first and fourth embodiments are referred to. As in the fourth embodiment, since the feeding point is set to one point (a pair) for each of the pair of electrodes 2 and 4, the substrate size is limited to about 1200 mm × 300 mm. However, it goes without saying that the size range can be expanded by increasing the number of feeding points.

Moreover, according to the said Example 5, in the power supply frequency 30MHz-100MHz, it is possible to obtain a remarkably favorable film thickness distribution compared with the conventional apparatus and method. This means that the industrial value related to productivity improvement and cost reduction in the manufacturing field of a-Si solar cells, thin film transistors, and photosensitive drums is remarkably large.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows the whole plasma surface treatment apparatus concerning Example 1 regarding this invention. FIG. 3 is an explanatory diagram illustrating a first specific example of a balance-unbalance conversion apparatus that is one configuration of the plasma surface treatment apparatus of FIG. 1 according to the first embodiment. FIG. 3 is an explanatory diagram illustrating a configuration of a connection portion between a tubular conductor and a cylindrical conductor, which is a constituent member of a first specific example of the balance-unbalance conversion apparatus in the plasma surface treatment apparatus of FIG. 1 according to the first embodiment. Explanatory drawing which shows the structure of the 2nd specific example of the balance-unbalance conversion apparatus which is one structure of the plasma surface treatment apparatus concerning Example 2 regarding this invention. The block diagram of the plasma surface treatment apparatus concerning Example 3 regarding this invention. FIG. 6 is an explanatory diagram showing an ideal configuration of a balance-unbalance conversion device that is one configuration of the plasma surface treatment device of FIG. 5 according to the third embodiment. Schematic which shows the whole plasma surface treatment apparatus concerning Example 4 regarding this invention. FIG. 9 is an explanatory diagram illustrating a fourth specific example of a balance-unbalance conversion apparatus that is one configuration of the plasma surface treatment apparatus of FIG. 7 according to the fourth embodiment. Explanatory drawing which shows the 5th example of the balance-unbalance conversion apparatus which is one structure of the plasma surface treatment apparatus concerning Example 5 regarding this invention. Explanatory drawing which shows the structure of the 1st typical example of the conventional plasma surface treatment apparatus. Explanatory drawing which shows the structure of the 2nd typical example of the conventional plasma surface treatment apparatus. Explanatory drawing which shows the structure of the 3rd typical example of the conventional plasma surface treatment apparatus. Explanatory drawing which shows the structure of the conventional super top type | mold balance-unbalance conversion apparatus. Explanatory drawing which shows the structure of the conventional half-wavelength detour-type balance-unbalance conversion apparatus.

Explanation of symbols

1. . . Vacuum vessel,
2. . . A first ungrounded electrode;
3. . . Substrate heater (not shown),
4). . . A second ungrounded electrode,
5a, 5b. . . Insulator support material not shown,
6). . . Small holes,
7). . . Earth shield,
8a, 8b. . . Discharge gas supply pipe,
9. . . Rectifying hole not shown,
10. . . Exhaust pipe,
11. . . Vacuum pump not shown,
12 . . substrate,
13. . . Gate valve not shown,
14 . . High frequency power supply,
15. . . coaxial cable,
16. . . Impedance matcher,
17a, 17b. . . First and second power supply locations;
18a, 18b. . . First and second feeder lines,
100. . . A first example of a balance-unbalance conversion device;
109b. . . Second coaxial cable.

Claims (9)

A vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, a first electrode on which a substrate is set, and a second electrode disposed opposite to the first electrode A pair of electrodes composed of electrodes; a power supply system that supplies high-frequency power to the pair of electrodes; and a balance-unbalance conversion device that is used in combination with the power supply system. A plasma generation balance-unbalance conversion apparatus used in a plasma surface treatment apparatus for treating a surface, wherein a coaxial conductor having a length of a quarter of the wavelength of the high-frequency power is covered on a feeding end side of a coaxial cable. , Dividing the super-top type balance-unbalance converter having a structure in which the center of the bottom surface of the cylindrical conductor is in close contact with the outer conductor of the coaxial cable, Before It is arranged inside the vacuum vessel, the other is arranged on the atmosphere side, and both are connected in the form of returning to the original state via a coaxial cable connection terminal attached to the wall of the vacuum vessel, and on the atmosphere side A balanced / unbalanced conversion apparatus for high-frequency plasma generation, characterized in that a length adjusting means is provided in the split-top type balanced / unbalanced conversion apparatus. A vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, a first electrode on which a substrate is set, and a second electrode disposed opposite to the first electrode A pair of electrodes composed of electrodes; a power supply system that supplies high-frequency power to the pair of electrodes; and a balance-unbalance conversion device that is used in combination with the power supply system. A plasma generation balance-unbalance conversion apparatus used in a plasma surface treatment apparatus for treating a surface, a flange disposed on a wall of the vacuum vessel, a metal core rod used in combination with the flange, and a first dielectric The metal core rod on the vacuum side surface of the coaxial cable connection terminal for a vacuum device comprising the body, the first tubular conductor, the second dielectric, the second tubular conductor, and the third dielectric, and the first 1 tube conductor, respectively The second tubular conductor on the vacuum side surface of the coaxial cable connection terminal for the vacuum apparatus is connected to the core wire and the outer conductor at one end of the first coaxial cable surrounded by the third tubular conductor. One end of the third tubular conductor is connected to the metal core rod on the atmospheric side of the coaxial cable connection terminal for the vacuum device and the first tubular conductor, respectively. A core wire at one end of the second coaxial cable surrounded by the tubular conductor and the cylindrical conductor and the outer conductor are connected, and the second tubular type on the atmospheric side of the coaxial cable connection terminal for vacuum device One end of the fourth tubular conductor is connected to the conductor, and the other end of the fourth tubular conductor and the one end of the cylindrical conductor are the inner cylinder and the outer cylinder. The other end of the cylindrical conductor is in close contact with the outer conductor of the second coaxial cable. And the distance from the end face of the first coaxial cable to the flange is equal to the distance from the end face of the third tubular conductor to the flange, and the outside of the first coaxial cable. The conductor and the third tubular conductor are arranged so as not to short-circuit, and the distance from the other end of the third tubular conductor to the closed end face of the cylindrical conductor is the high-frequency power. Of the second coaxial cable and the other end of the second coaxial cable and the outer conductor as an input section, and the other core wire and the outer conductor of the first coaxial cable as an output section. A balance-unbalance conversion apparatus for high-frequency plasma generation, characterized in that it has a configuration of A vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, a first electrode on which a substrate is set, and a second electrode disposed opposite to the first electrode A pair of electrodes composed of electrodes; a power supply system that supplies high-frequency power to the pair of electrodes; and a balance-unbalance conversion device that is used in combination with the power supply system. A plasma generation balance-unbalance conversion apparatus used in a plasma surface treatment apparatus for treating a surface, a flange disposed on a wall of the vacuum vessel, a metal core rod used in combination with the flange, and a first dielectric The metal core rod on the vacuum side of the coaxial cable connection terminal for a vacuum apparatus, comprising the body, the first tubular conductor, the second dielectric, and the second tubular conductor in close contact with the flange; First tube-type conductivity Are connected to the core wire and the outer conductor of one end of the first coaxial cable surrounded by the second tubular conductor, respectively, and the metal on the atmospheric side of the coaxial cable connection terminal for the vacuum device The core wire and the outer conductor at one end of the second coaxial cable surrounded by the second tubular conductor and the cylindrical conductor are connected to the core-making rod and the first tubular conductor, respectively. The end portion of the second tubular conductor and the end portion on the open side of the cylindrical conductor are brought into close contact with each other so as to have a relationship between the inner cylinder and the outer cylinder, and the central portion of the bottom surface of the cylindrical conductor Is closely attached to the outer conductor of the second coaxial cable so that the distance from the end surface of the first coaxial cable to the flange is equal to the distance from the end surface of the second tubular conductor to the flange. In addition, the outer conductor of the first coaxial cable and the second tubular conductor are not short-circuited. The distance from the open end surface of the second tubular conductor to the bottom surface of the cylindrical conductor is a quarter of the wavelength of the high-frequency power supplied from the high-frequency power source. And having a configuration in which the core wire and the outer conductor at the other end of the second coaxial cable are used as an input portion, and the other core wire and the outer conductor of the first coaxial cable are used as an output portion. A balanced / unbalanced converter for high-frequency plasma generation. A vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, a first electrode on which a substrate is set, and a second electrode disposed opposite to the first electrode A pair of electrodes composed of electrodes; a power supply system that supplies high-frequency power to the pair of electrodes; and a balance-unbalance conversion device that is used in combination with the power supply system. A balance-unbalance conversion device for plasma generation used in a plasma surface treatment apparatus for treating a surface, wherein core wires at one end of two coaxial cables having the same length are provided on the pair of electrodes. Connect to the power supply point, short-circuit the outer conductor of each coaxial cable at the end, and place it on the core wire and outer conductor at the other end of the two coaxial cables, respectively, on the wall of the vacuum vessel Same Supplying power via the cable connection terminal, the high-frequency plasma generation balun apparatus characterized by having a structure that means are provided for setting the phase difference between the voltage of the power to 180 degrees. A vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, a first electrode on which a substrate is set, and a second electrode disposed opposite to the first electrode A pair of electrodes composed of electrodes; a power supply system that supplies high-frequency power to the pair of electrodes; and a balance-unbalance conversion device that is used in combination with the power supply system. A balance-unbalance converter for plasma generation used in a plasma surface treatment apparatus for treating a surface, wherein the length is L on the atmosphere side surface of the first coaxial cable connection terminal for vacuum equipment disposed on the wall of the vacuum vessel. One end of the first coaxial cable is connected, and the other end of the first coaxial cable is connected to a first output terminal of the coaxial cable branch, and the first end of the coaxial cable branch is The length of the two output terminals One end of the second coaxial cable having a length equal to a value obtained by adding the length L of the first coaxial cable to one half of the wavelength λ of the high frequency power, that is, (λ / 2 + L) is connected. The other end of the second coaxial cable is connected to the atmosphere side surface of the second coaxial cable connection terminal for vacuum equipment disposed on the wall of the vacuum vessel, and the second coaxial cable is connected to the input terminal of the coaxial cable branching device. One end of the third coaxial cable is connected, and the core wire and the outer conductor of the other end of the third coaxial cable are used as input parts, and the vacuum of the coaxial cable connection terminals for the first and second vacuum devices is used. One end of each of the fourth and fifth coaxial cables having the same length is connected to the side surface, and each outer conductor of the other end of the fourth and fifth coaxial cables is connected to the high-frequency power. Shorted by a short-circuiting conductor with a length of one-third or less of the wavelength And high-frequency plasma generation balun apparatus characterized by having a configuration in which an output portion of each core wire of an end portion of the fourth and fifth coaxial cable. A vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, a first electrode on which a substrate is set, and a second electrode disposed opposite to the first electrode A pair of electrodes composed of electrodes; a power supply system that supplies high-frequency power to the pair of electrodes; and a balance-unbalance conversion device that is used in combination with the power supply system. A balance-unbalance converter for plasma generation used in a plasma surface treatment apparatus for treating a surface, wherein a coaxial cable branch is formed on the atmosphere side surface of a first vacuum device coaxial cable connection terminal disposed on a wall of the vacuum vessel. A second output terminal of the coaxial cable branch is connected to one end of a second coaxial cable having a length that is half the wavelength λ of the high-frequency power. Connected, the second The other end of the coaxial cable is connected to the atmospheric side surface of the second coaxial cable connection terminal for vacuum equipment disposed on the wall of the vacuum vessel, and the input terminal of the coaxial cable branch is connected to the input terminal of the first coaxial cable. One end is connected, the core of the other end of the first coaxial cable and the outer conductor as an input, and the vacuum side of the first and second vacuum device coaxial cable connection terminal, respectively, One ends of the third and fourth coaxial cables having the same length are connected to each other, and the outer conductors at the other ends of the third and fourth coaxial cables are 30% of the wavelength of the high-frequency power. A high-frequency plasma generation characterized in that it is short-circuited by a short-circuiting conductor having a length of 1 or less and the core wires at the ends of the third and fourth coaxial cables are used as output portions. Balance / unbalance conversion device. A vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, a first electrode on which a substrate is set, and a second electrode disposed opposite to the first electrode A pair of electrodes composed of electrodes; a power supply system that supplies high-frequency power to the pair of electrodes; and a balance-unbalance conversion device that is used in combination with the power supply system. A plasma generation balance-unbalance conversion device used in a plasma surface treatment apparatus for treating a surface, wherein an input terminal of the LC bridge-type balance-unbalance conversion device is used as an input unit, and the LC bridge-type balance-unbalance conversion device 2 One end of each of the first and second atmospheric coaxial cables having the same length is connected to each of the two output terminals, and the other ends of the first and second atmospheric coaxial cables are respectively connected to the first output terminal. 1st and 2nd And connected to one end of the first and second vacuum coaxial cables via the coaxial cable connection terminal for the vacuum device, and the other end of the first and second vacuum coaxial cables. The outer conductor is short-circuited by a short-circuiting conductor having a length of one-third or less of the wavelength of the high-frequency power, and each core wire at the end portion is used as an output portion. A balance-unbalance converter for high-frequency plasma generation. A vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, a first electrode on which a substrate is set, and a second electrode disposed opposite to the first electrode A pair of electrodes composed of electrodes; a power supply system that supplies high-frequency power to the pair of electrodes; and a balance-unbalance conversion device that is used in combination with the power supply system. A plasma surface treatment apparatus for treating a surface, wherein the balance-unbalance conversion device is constituted by the balance-unbalance conversion device for high-frequency plasma generation according to any one of claims 1 to 7. Surface treatment equipment. A vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, a first electrode on which a substrate is set, and a second electrode disposed opposite to the first electrode A pair of electrodes composed of electrodes; a power supply system that supplies high-frequency power to the pair of electrodes; and a balance-unbalance conversion device that is used in combination with the power supply system. In the plasma surface treatment method for treating a surface, the balance-unbalance conversion device is constituted by the balance-unbalance conversion device for high-frequency plasma generation according to any one of claims 1 to 7, and the plasma surface treatment is performed. A plasma surface treatment method.

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